The effects of alloying elements on zincate treatment and adhesion of electroless Ni-P coating onto various aluminum alloy substrates were examined.Surface morphology of zinc deposits in the 1st zincate treatment and ...The effects of alloying elements on zincate treatment and adhesion of electroless Ni-P coating onto various aluminum alloy substrates were examined.Surface morphology of zinc deposits in the 1st zincate treatment and its adhesion were changed depending on the alloying element.The zinc deposits in the 2nd zincate treatment became thinly uniform,and the adhesion between aluminum alloy substrate and Ni-P coating was improved irrespective of the alloying element.XPS analysis revealed the existence of zinc on the surface of each aluminum alloy substrate after the pickling in 5% nitric acid.This zinc on the surface should be an important factor influencing the morphology of zinc deposit at the 2nd zincate treatment and its adhesion.展开更多
A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were...A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.展开更多
Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological p...Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.展开更多
Electroless deposition has been used to deposit Ni-P films on glass slides using the reducing agent sodium hypophosphite. This has been done with a purpose to use Ni-P films as back contact for silicon carbide radiati...Electroless deposition has been used to deposit Ni-P films on glass slides using the reducing agent sodium hypophosphite. This has been done with a purpose to use Ni-P films as back contact for silicon carbide radiation detectors. By keeping deposition time, temperature, pH and concentration of the precursor solution constant, the film deposition has been done. XPS studies were done to analyze the composition and stoichiometry of Ni-P thin films.展开更多
A mechanically assisted electroless barrel-plating Ni-P was carried out in a rolling drum containing Mg alloy specimens and ceramic balls, which was submerged in a bath containing electroless plating solution deposite...A mechanically assisted electroless barrel-plating Ni-P was carried out in a rolling drum containing Mg alloy specimens and ceramic balls, which was submerged in a bath containing electroless plating solution deposited by this novel technique have a It is demonstrated that the Ni-P coatings crystallized Ni-P solid solution structure, showing fine-grains, higher hardness, and higher corrosion resistance compared with the conventional electroless plated amorphous Ni-P coatings. After heat treatment at 400 ℃ for 1 h, the structure of such Ni-P coatings were transformed to a structure with Ni-Ni3P double phases, and cracks in these coatings could not be observed, whereas cracks appeared seriously in the conventional electroless plated Ni-P coating after same heat treatment. Therefore, both hardness and corrosion resistance of these Ni-P coatings can be improved further by heat treatment. All of these beneficial effects can be attributed to the role of mechanical attrition during the mechanically assisted electroless barrel-plating process.展开更多
Nickel-phosphorus (Ni-P) composite coatings containing potassium titanate (K2Ti6O13) whiskers (PTWs) were prepared by electroless plating. The surface morphology and component of coatings were investigated by sc...Nickel-phosphorus (Ni-P) composite coatings containing potassium titanate (K2Ti6O13) whiskers (PTWs) were prepared by electroless plating. The surface morphology and component of coatings were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively before and after wear test. The tribological performance was evaluated using a pin-on-disk wear tester under dry conditions. It is found that the Ni-P-PTWs composite coatings exhibit higher wear resistance than Ni-P and Ni-P-SiC electroless coatings. The favorable effects of PTWs on the tribological properties of the composite coatings are attributed to the super-strong mechanical properties and the specific tunneling structures of PTWs. The PTWs greatly reinforce the structure of the Ni-P-based composite coatings and thereby greatly reduce the adhesive and plough wear of Ni-P-PTWs composite coatings.展开更多
Three kinds of Ni-P electroless coatings were prepared in nickel sulphate solution at different pH values of 4.5, 5.5 and 6.5 with the purpose of ascertaining the influence of pH value on microstructure, internal stre...Three kinds of Ni-P electroless coatings were prepared in nickel sulphate solution at different pH values of 4.5, 5.5 and 6.5 with the purpose of ascertaining the influence of pH value on microstructure, internal stress statue and thermal stability of the coatings. Laser curvature (LC) method was used to measure the residual stress level in the coatings. Scanning electronic microscopy (SEM) and transmission electronic microscopy with energy dispersive spectrum (TEM/EDS) were used to examine the surface morphology and internal phase structure of the coatings, respectively. Differential scanning calorimeter (DSC) was used to analyze the phase transformation and thermal stability of the coatings at high temperature. Results showed the NiP coating prepared at pH 5.5 with nanocrystal mixed in amorphous structure had the worst thermal stability. The relatively higher stability of Ni-P coatings prepared at pH 4.5 and 6.5 was ascribed to the lower tensile stress level and much finer grain size, respectively. Besides, inverse Hall-Petch effect of annealing strengthening might also contribute to the integrity of NiP coating prepared at pH 6.5. C 2009 Hui Ming Jin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
In order to improve the surface performance and increase the lifetime of P 110 oil casing tube steel during operation, electroless plating was conducted to form Ni-P coating onto its surface. The surface morphology/el...In order to improve the surface performance and increase the lifetime of P 110 oil casing tube steel during operation, electroless plating was conducted to form Ni-P coating onto its surface. The surface morphology/element distribution and phase constitution of the Ni-P coating were analyzed using scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Tribological and electrochemical measurement tests were applied to investigate the wear and corrosion resistance of P110 steel and the Ni-P coating. The results showed that a uniform and compact, high phosphorous Ni-P coating was formed. The obtained Ni-P coating indicated certain friction-reduction effect and lower mass loss during friction-wear tests. The Ni-P coating also exhibited higher corrosion resistance in comparison with bared P 110 steel. The obtained N i-P coating has significantly improved the surface performance of P110 steel.展开更多
Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart. Scanning electronic microscopy (SEM) and X-r...Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart. Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) spectrometer were used to examine surface morphology and structure of the as-plated coating. Differential scanning calorimeter (DSC) and transmission electronic microscopy (TEM) were used to study the coating's phase change at high temperature. The coating's corrosive behavior in 3%NaCl + 5%H2SO4 solution was also investigated. The results showed that Ni-P coating had partial amorphous structure mixed with nano-crystals, while the Ni-P/CeO2 coating had perfect amorphous structure. In high-temperature condition, Ni3P precipitation and Ni crystallization took place in both coatings but at different temperatures, while the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels. The anti-corrosion property was better in the CeO2-containing coating, and this was due to its less liability to undergo local-cell corrosion than its CeO2-free counterpart. Ni-P/CeO2 coating's pure amorphous structure was the result of Ni's hindered crystal-typed deposition and P's promoted deposition.展开更多
The addition of superelastic NiTi to electroless Ni-P coating has been found to toughen the otherwise brittle coatings in static loading conditions, though its effect on erosion behaviour has not yet been explored. In...The addition of superelastic NiTi to electroless Ni-P coating has been found to toughen the otherwise brittle coatings in static loading conditions, though its effect on erosion behaviour has not yet been explored. In the present study, spherical WC-Co erodent particles were used in single particle impact testing of Ni-P-nano-NiTi composite coatings on API X100 steel substrates at two average velocities—35 m/s and 52 m/s. Erosion tests were performed at impact angles of 30°, 45°, 60°, and 90°. The effect of NiTi concentration in the coating was also examined. Through examination of the impact craters and material response at various impact conditions, it was found that the presence of superelastic NiTi in the brittle Ni-P matrix hindered the propagation of cracks and provided a barrier to crack growth. The following toughening mechanisms were identified: crack bridging and deflection, micro-cracking, and transformation toughening.展开更多
Ni-P matrix composite coating reinforced by carbon nanotubes (CNTs) was deposit ed by electroless plating. The most important factors that influence the content of carbon nanotubes in deposits,such as agitation,surfac...Ni-P matrix composite coating reinforced by carbon nanotubes (CNTs) was deposit ed by electroless plating. The most important factors that influence the content of carbon nanotubes in deposits,such as agitation,surfactant and carbon nanot ubes concentration in the plating bath were investigated. The surface morphology,structure and properties of the Ni-P-CNTs coating were examined. It is found that the maximum content of carbon nanotubes in the deposits is independent of carbon nanotubes concentration in the plating bath when it is up to 5 mg/L. The test results show that the carbon nanotubes co-deposited do not change the str ucture of the Ni-P matrix of the composite coating,but greatly increase the ha rdness and wear resistance and decrease the friction coefficient of the Ni-P-C NTs composite coating with increasing content of carbon nanotubes in deposits.展开更多
Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart. Scanning electronic microscopy (SEM), transm...Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and differential scanning calorimeter (DSC) were used to examine surface morphology and microstructure of the coating. Aqueous corrosion was done in 3%NaCl+5%H2SO4 solution and high temperature oxidation was done at 750 ℃ in air. The results showed that Ni-P coating had partial amorphous structure mixed with nano-crystals, while the Ni-P/CeO2 coating had perfect amorphous structure. At high temperature, Ni3P precipitation and Ni crystallization took place in both coatings at different temperatures. Aqueous corrosion property and high temperature oxidation property of the composite coating were remarkably improved due to the coating's microstructure change and the rare earth doping effect. During the co-deposition process, some Ce^n+(n=3, 4) ions may be adsorbed to metal/solution interface and hinder nickel deposition. Ni-P/CeO2 coating's perfect amorphous structure results from the hindered crystal-typed deposition of nickel and the promoted deposition of phosphorous.展开更多
The wear behaviour of composite coatings is related to the nature of embedded particles.The effects of particle size on the wear behaviour of composite coatings are analyzed.Electroless nickel composite coatings conta...The wear behaviour of composite coatings is related to the nature of embedded particles.The effects of particle size on the wear behaviour of composite coatings are analyzed.Electroless nickel composite coatings containing diamond particles with the sizes in the range of 0—0.5,0.5—1,1—2μm are prepared.The surface morphology of diamond particles and composite coatings are observed by scanning electron microscopy(SEM).The wear tests of composite coatings are comparatively evaluated by sliding against a cemented tungsten carbide ball.The 3D morphology of worn scar is evaluated by using a 3Dprofiler.The results show that the hardness and wear resistance of composite coatings can increase with the increase of particle sizes.The mixture mechanism of adhesive wear and abrasive wear turn into single abrasive wear with the increase of particle sizes as well.The transformation of wear behaviour is mainly attributed to particle roles during wear process.展开更多
The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,struc...The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .展开更多
Flame Thermal Spray (FTS) coatings frequently show some porosity and reduced adherence to substrate, which affect its properties, especially its corrosion resistance. In this work, the corrosion resistance of AISI 101...Flame Thermal Spray (FTS) coatings frequently show some porosity and reduced adherence to substrate, which affect its properties, especially its corrosion resistance. In this work, the corrosion resistance of AISI 1018 carbon steel coated by different methods is compared: electroless nickel (EN) coating, NiCrFeBSi obtained by FTS, duplex coatings of an EN deposit on a layer of NiCrFeBSi obtained by FTS and a layer of NiCrFeBSi on an EN deposit. The coatings were characterized using optical microscopy and scanning electron microscopy techniques, EDS microprobe microanalysis, roughness as well as electrochemical polarization tests to obtain the corrosion rate. The results show the enhancement in the corrosion resistance in saline medium of the duplex coatings, especially of the EN coating on FTS layer.展开更多
The corrosion resistance of nickel-phosphorus (Ni-P) coatings and their mechanical properties in seawater have led inestigations into the development of new technologies and the replacement of some special alloys in e...The corrosion resistance of nickel-phosphorus (Ni-P) coatings and their mechanical properties in seawater have led inestigations into the development of new technologies and the replacement of some special alloys in equipment used in oil production, such as valves, tubing, sucker rod joints, pumps, riser, manifolds and subsea Christmas trees. These studies began with Brenner and Riddel who developed, in the 1940s, formulations for Ni-P deposition on carbon steel without using an electric current. Joint deposition of nickel and phosphorus on a metallic surface (carbon steel) without applying an external current is accomplished using cathodic reduction with hydrogen (H) from a reducing agent (sodium hypophosphite) and nickel salts. To assure good performance of a Ni-P coating, the deposit quality must be inspected and evaluated during the chemical deposition process or in the end product. The recommended test parameters are: thickness, layer uniformity, hardness, adhesion, porosity, corrosion resistance and chemical composition of the nickel-phosphorus coating. The purpose of this paper was to investigate the Ni-P coating process, to evaluate the b?haviour of Ni-P in a saline environment using aqueous brine (3.5% - 30% sodium chloride by mass) and to present possible defects that could compromise the coating.展开更多
There are many factors that affect the phosphorus content in the electroless Ni-P coatings The effects of the compositions of plating solution,the PH values of plat ing solution and the deposition temperature on the p...There are many factors that affect the phosphorus content in the electroless Ni-P coatings The effects of the compositions of plating solution,the PH values of plat ing solution and the deposition temperature on the phosphorus content in Ni-P coatings were investigated in this paper It is found that the phosphorus content in Ni-P coatings increases and the deposition rate decreases with decreasing PH values,nickel sulphate NiSO4 content of plating solution and the deposition temperature.展开更多
To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum (Co-B/M) nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of amm...To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum (Co-B/M) nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of ammonium perchlorate (AP) and AP-based solid state propellants. X-ray diffractometry (XRD), scanning electron microscopy (SEM), inductive coupled plasma emission spectrometry (ICP), differential scanning calorimetry (DSC) as well as strand burner method were employed to characterize the crystal phase, morphologies, chemical composition, and catalytic activity of the as-synthesized material. The results show that a continuous layer of about 100 nm amorphous Co72.6B27.4 covers the surfaces of M particles. Addition of the as-synthesized Co-B/A1 nanocomposites as catalysts promotes AP decomposition, enhances the burning rate, and lowers the pressure exponent of the AP-based propellants considerably.展开更多
Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart.Scanning electronic microscopy(SEM), transmis...Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart.Scanning electronic microscopy(SEM), transmission electronic microscopy(TEM), X-ray diffraction spectrometer(XRD), and differential scanning calorimeter(DSC) were used to examine surface morphology and microstructure of the coating.Corrosive investigation was carried out in 3%NaCl+5%H2SO4 solution.The results showed that Ni-P coating had partial amorphous structure mixed with nanocrystals, whereas the Ni-P/CeO2 coating had perfect amorphous structure.In high temperature condition, Ni3P precipitation and Ni crystallization occurred in both coatings but at different temperatures, whereas the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels.The anticorrosion property and passivity were improved in the CeO2-containing coating due to its less liability to undergo local-cell corrosion than its CeO2-free counterpart.During the co-deposition process, some Cen+(n=3, 4) ions may be adsorbed to the metal/solution interface, hinder nickel's crystal-typed deposition and promote phosphorous deposition.The nano-CeO2 doping finally resulted in the coating' perfect amorphous structure and good anti-corrosive property.展开更多
文摘The effects of alloying elements on zincate treatment and adhesion of electroless Ni-P coating onto various aluminum alloy substrates were examined.Surface morphology of zinc deposits in the 1st zincate treatment and its adhesion were changed depending on the alloying element.The zinc deposits in the 2nd zincate treatment became thinly uniform,and the adhesion between aluminum alloy substrate and Ni-P coating was improved irrespective of the alloying element.XPS analysis revealed the existence of zinc on the surface of each aluminum alloy substrate after the pickling in 5% nitric acid.This zinc on the surface should be an important factor influencing the morphology of zinc deposit at the 2nd zincate treatment and its adhesion.
基金financially supported by the National Natural Science Foundation of China (No.52271073)。
文摘A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.
基金Supported by Sichuan Provincial Science and Technology Program of China(Grant No.2018JY0245)National Natural Science Foundation of China(Grant No.51975492)Natural Science Foundation of Southwest University of Science and Technology of China(Grant No.19xz7163).
文摘Titanium alloys are excellent structural materials in engineering fields,but their poor tribological properties limit their further applications.Electroless plating is an effective method to enhance the tribological performance of alloys,but it is difficult to efficiently apply to titanium alloys,due to titanium alloy’s strong chemical activity.In this work,the electroless Nickel-Boron(Ni-B)coating was successfully deposited on the surface of titanium alloy(Ti-6AL-4V)via a new pre-treatment process.Then,linearly reciprocating sliding wear tests were performed to evaluate the tribological behaviors of titanium alloy and its electroless Ni-B coatings.It was found that the Ni-B coatings can decrease the wear rate of the titanium alloy from 19.89×10^(−3)mm^(3)to 0.41×10^(−3)mm^(3),which attributes to the much higher hardness of Ni-B coatings.After heat treatment,the hardness of Ni-B coating further increases corresponding to coating crystallization and hard phase formation.However,heat treatment does not improve the tribological performance of Ni-B coating,due to the fact that higher brittleness and more severe oxidative wear exacerbate the damage of heat-treated coatings.Furthermore,the Ni-B coatings heat-treated both in air and nitrogen almost present the same tribological performance.The finding of this work on electroless coating would further extend the practical applications of titanium alloys in the engineering fields.
文摘Electroless deposition has been used to deposit Ni-P films on glass slides using the reducing agent sodium hypophosphite. This has been done with a purpose to use Ni-P films as back contact for silicon carbide radiation detectors. By keeping deposition time, temperature, pH and concentration of the precursor solution constant, the film deposition has been done. XPS studies were done to analyze the composition and stoichiometry of Ni-P thin films.
基金supported by the National Natural Science Foundation of China (Grant No.50671006)the National R&D Infrastructure and Facility Development Program of China (2005DKA10400-Z1)
文摘A mechanically assisted electroless barrel-plating Ni-P was carried out in a rolling drum containing Mg alloy specimens and ceramic balls, which was submerged in a bath containing electroless plating solution deposited by this novel technique have a It is demonstrated that the Ni-P coatings crystallized Ni-P solid solution structure, showing fine-grains, higher hardness, and higher corrosion resistance compared with the conventional electroless plated amorphous Ni-P coatings. After heat treatment at 400 ℃ for 1 h, the structure of such Ni-P coatings were transformed to a structure with Ni-Ni3P double phases, and cracks in these coatings could not be observed, whereas cracks appeared seriously in the conventional electroless plated Ni-P coating after same heat treatment. Therefore, both hardness and corrosion resistance of these Ni-P coatings can be improved further by heat treatment. All of these beneficial effects can be attributed to the role of mechanical attrition during the mechanically assisted electroless barrel-plating process.
基金This work was supported by the National Natural Science Foundation of China(Grant No.50335060)the Excellent Young Teacher Award of the Education Ministry of China(No.[2002]383).
文摘Nickel-phosphorus (Ni-P) composite coatings containing potassium titanate (K2Ti6O13) whiskers (PTWs) were prepared by electroless plating. The surface morphology and component of coatings were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), respectively before and after wear test. The tribological performance was evaluated using a pin-on-disk wear tester under dry conditions. It is found that the Ni-P-PTWs composite coatings exhibit higher wear resistance than Ni-P and Ni-P-SiC electroless coatings. The favorable effects of PTWs on the tribological properties of the composite coatings are attributed to the super-strong mechanical properties and the specific tunneling structures of PTWs. The PTWs greatly reinforce the structure of the Ni-P-based composite coatings and thereby greatly reduce the adhesive and plough wear of Ni-P-PTWs composite coatings.
文摘Three kinds of Ni-P electroless coatings were prepared in nickel sulphate solution at different pH values of 4.5, 5.5 and 6.5 with the purpose of ascertaining the influence of pH value on microstructure, internal stress statue and thermal stability of the coatings. Laser curvature (LC) method was used to measure the residual stress level in the coatings. Scanning electronic microscopy (SEM) and transmission electronic microscopy with energy dispersive spectrum (TEM/EDS) were used to examine the surface morphology and internal phase structure of the coatings, respectively. Differential scanning calorimeter (DSC) was used to analyze the phase transformation and thermal stability of the coatings at high temperature. Results showed the NiP coating prepared at pH 5.5 with nanocrystal mixed in amorphous structure had the worst thermal stability. The relatively higher stability of Ni-P coatings prepared at pH 4.5 and 6.5 was ascribed to the lower tensile stress level and much finer grain size, respectively. Besides, inverse Hall-Petch effect of annealing strengthening might also contribute to the integrity of NiP coating prepared at pH 6.5. C 2009 Hui Ming Jin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
基金Funded by the China Postdoctoral Science Foundation(No.2012M520604)the Natural Science Foundation for Young Scientists of Shanxi Province(No.2013021013-2)
文摘In order to improve the surface performance and increase the lifetime of P 110 oil casing tube steel during operation, electroless plating was conducted to form Ni-P coating onto its surface. The surface morphology/element distribution and phase constitution of the Ni-P coating were analyzed using scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Tribological and electrochemical measurement tests were applied to investigate the wear and corrosion resistance of P110 steel and the Ni-P coating. The results showed that a uniform and compact, high phosphorous Ni-P coating was formed. The obtained Ni-P coating indicated certain friction-reduction effect and lower mass loss during friction-wear tests. The Ni-P coating also exhibited higher corrosion resistance in comparison with bared P 110 steel. The obtained N i-P coating has significantly improved the surface performance of P110 steel.
基金supported by National Natural Science Foundation of China (No.29233011)Natural Science Foundation of Jiangsu Province (No.07KJD430246).
文摘Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart. Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) spectrometer were used to examine surface morphology and structure of the as-plated coating. Differential scanning calorimeter (DSC) and transmission electronic microscopy (TEM) were used to study the coating's phase change at high temperature. The coating's corrosive behavior in 3%NaCl + 5%H2SO4 solution was also investigated. The results showed that Ni-P coating had partial amorphous structure mixed with nano-crystals, while the Ni-P/CeO2 coating had perfect amorphous structure. In high-temperature condition, Ni3P precipitation and Ni crystallization took place in both coatings but at different temperatures, while the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels. The anti-corrosion property was better in the CeO2-containing coating, and this was due to its less liability to undergo local-cell corrosion than its CeO2-free counterpart. Ni-P/CeO2 coating's pure amorphous structure was the result of Ni's hindered crystal-typed deposition and P's promoted deposition.
文摘The addition of superelastic NiTi to electroless Ni-P coating has been found to toughen the otherwise brittle coatings in static loading conditions, though its effect on erosion behaviour has not yet been explored. In the present study, spherical WC-Co erodent particles were used in single particle impact testing of Ni-P-nano-NiTi composite coatings on API X100 steel substrates at two average velocities—35 m/s and 52 m/s. Erosion tests were performed at impact angles of 30°, 45°, 60°, and 90°. The effect of NiTi concentration in the coating was also examined. Through examination of the impact craters and material response at various impact conditions, it was found that the presence of superelastic NiTi in the brittle Ni-P matrix hindered the propagation of cracks and provided a barrier to crack growth. The following toughening mechanisms were identified: crack bridging and deflection, micro-cracking, and transformation toughening.
文摘Ni-P matrix composite coating reinforced by carbon nanotubes (CNTs) was deposit ed by electroless plating. The most important factors that influence the content of carbon nanotubes in deposits,such as agitation,surfactant and carbon nanot ubes concentration in the plating bath were investigated. The surface morphology,structure and properties of the Ni-P-CNTs coating were examined. It is found that the maximum content of carbon nanotubes in the deposits is independent of carbon nanotubes concentration in the plating bath when it is up to 5 mg/L. The test results show that the carbon nanotubes co-deposited do not change the str ucture of the Ni-P matrix of the composite coating,but greatly increase the ha rdness and wear resistance and decrease the friction coefficient of the Ni-P-C NTs composite coating with increasing content of carbon nanotubes in deposits.
基金Funded by the National Natural Science Foundation of China (No.59231011)the National Natural Science Foundation of Colombia (No.M018327)
文摘Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and differential scanning calorimeter (DSC) were used to examine surface morphology and microstructure of the coating. Aqueous corrosion was done in 3%NaCl+5%H2SO4 solution and high temperature oxidation was done at 750 ℃ in air. The results showed that Ni-P coating had partial amorphous structure mixed with nano-crystals, while the Ni-P/CeO2 coating had perfect amorphous structure. At high temperature, Ni3P precipitation and Ni crystallization took place in both coatings at different temperatures. Aqueous corrosion property and high temperature oxidation property of the composite coating were remarkably improved due to the coating's microstructure change and the rare earth doping effect. During the co-deposition process, some Ce^n+(n=3, 4) ions may be adsorbed to metal/solution interface and hinder nickel deposition. Ni-P/CeO2 coating's perfect amorphous structure results from the hindered crystal-typed deposition of nickel and the promoted deposition of phosphorous.
基金Supported by the National Natural Science Foundation of China(51175260)the Fundamental Research Funds for the Central Universities(NP2012506)the Open Fund of Jiangsu Province Key Laboratory for Materials Tribology(kjsmcx0901)
文摘The wear behaviour of composite coatings is related to the nature of embedded particles.The effects of particle size on the wear behaviour of composite coatings are analyzed.Electroless nickel composite coatings containing diamond particles with the sizes in the range of 0—0.5,0.5—1,1—2μm are prepared.The surface morphology of diamond particles and composite coatings are observed by scanning electron microscopy(SEM).The wear tests of composite coatings are comparatively evaluated by sliding against a cemented tungsten carbide ball.The 3D morphology of worn scar is evaluated by using a 3Dprofiler.The results show that the hardness and wear resistance of composite coatings can increase with the increase of particle sizes.The mixture mechanism of adhesive wear and abrasive wear turn into single abrasive wear with the increase of particle sizes as well.The transformation of wear behaviour is mainly attributed to particle roles during wear process.
基金Projects(05B008) supported by Scientific Research Fund of Hunan Provincial Education Departmentproject(104014) supported by Fok Ying Tong Education Foundation of Ministry of Education
文摘The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .
文摘Flame Thermal Spray (FTS) coatings frequently show some porosity and reduced adherence to substrate, which affect its properties, especially its corrosion resistance. In this work, the corrosion resistance of AISI 1018 carbon steel coated by different methods is compared: electroless nickel (EN) coating, NiCrFeBSi obtained by FTS, duplex coatings of an EN deposit on a layer of NiCrFeBSi obtained by FTS and a layer of NiCrFeBSi on an EN deposit. The coatings were characterized using optical microscopy and scanning electron microscopy techniques, EDS microprobe microanalysis, roughness as well as electrochemical polarization tests to obtain the corrosion rate. The results show the enhancement in the corrosion resistance in saline medium of the duplex coatings, especially of the EN coating on FTS layer.
文摘The corrosion resistance of nickel-phosphorus (Ni-P) coatings and their mechanical properties in seawater have led inestigations into the development of new technologies and the replacement of some special alloys in equipment used in oil production, such as valves, tubing, sucker rod joints, pumps, riser, manifolds and subsea Christmas trees. These studies began with Brenner and Riddel who developed, in the 1940s, formulations for Ni-P deposition on carbon steel without using an electric current. Joint deposition of nickel and phosphorus on a metallic surface (carbon steel) without applying an external current is accomplished using cathodic reduction with hydrogen (H) from a reducing agent (sodium hypophosphite) and nickel salts. To assure good performance of a Ni-P coating, the deposit quality must be inspected and evaluated during the chemical deposition process or in the end product. The recommended test parameters are: thickness, layer uniformity, hardness, adhesion, porosity, corrosion resistance and chemical composition of the nickel-phosphorus coating. The purpose of this paper was to investigate the Ni-P coating process, to evaluate the b?haviour of Ni-P in a saline environment using aqueous brine (3.5% - 30% sodium chloride by mass) and to present possible defects that could compromise the coating.
文摘There are many factors that affect the phosphorus content in the electroless Ni-P coatings The effects of the compositions of plating solution,the PH values of plat ing solution and the deposition temperature on the phosphorus content in Ni-P coatings were investigated in this paper It is found that the phosphorus content in Ni-P coatings increases and the deposition rate decreases with decreasing PH values,nickel sulphate NiSO4 content of plating solution and the deposition temperature.
基金supported by the National Natural Science Foundation of China (No. 50876046)
文摘To improve the catalytic activity of amorphous Co-B alloys, Co-B coated aluminum (Co-B/M) nanocomposites were prepared by electroless coating technique and evaluated as additives for the catalytic performance of ammonium perchlorate (AP) and AP-based solid state propellants. X-ray diffractometry (XRD), scanning electron microscopy (SEM), inductive coupled plasma emission spectrometry (ICP), differential scanning calorimetry (DSC) as well as strand burner method were employed to characterize the crystal phase, morphologies, chemical composition, and catalytic activity of the as-synthesized material. The results show that a continuous layer of about 100 nm amorphous Co72.6B27.4 covers the surfaces of M particles. Addition of the as-synthesized Co-B/A1 nanocomposites as catalysts promotes AP decomposition, enhances the burning rate, and lowers the pressure exponent of the AP-based propellants considerably.
基金supported by the National Natural Science Foundation of China (29233011)the Natural Science Foundation of Jiangsu Province (07KJD430246)
文摘Electroless Ni-P/nano-CeO2 composite coating was prepared in acidic condition, and its microstructure and corrosive property were compared with its CeO2-free counterpart.Scanning electronic microscopy(SEM), transmission electronic microscopy(TEM), X-ray diffraction spectrometer(XRD), and differential scanning calorimeter(DSC) were used to examine surface morphology and microstructure of the coating.Corrosive investigation was carried out in 3%NaCl+5%H2SO4 solution.The results showed that Ni-P coating had partial amorphous structure mixed with nanocrystals, whereas the Ni-P/CeO2 coating had perfect amorphous structure.In high temperature condition, Ni3P precipitation and Ni crystallization occurred in both coatings but at different temperatures, whereas the Ni-P/CeO2 coating had sintered phase of NiCe2O4 spinels.The anticorrosion property and passivity were improved in the CeO2-containing coating due to its less liability to undergo local-cell corrosion than its CeO2-free counterpart.During the co-deposition process, some Cen+(n=3, 4) ions may be adsorbed to the metal/solution interface, hinder nickel's crystal-typed deposition and promote phosphorous deposition.The nano-CeO2 doping finally resulted in the coating' perfect amorphous structure and good anti-corrosive property.